Battery charging and voltage regulating system



April 23, 1946.v K. MULLERHEIM 4 BATTERY CHARGING AND VOLTAGE REGULATINGSYSTEM Filed July l, '2 vSheets-Sheet l INVENToR.

KURT MULLERHEIM ATTORNEY April 23, 1946. KA MULLERHEIM 2,398,845

BATTERY CHARGING AND VOLTAGE REGULATING SYSTEM Filed July 1, 1944 2sheets-sheet 2 Patented Apr. 23, 1946 UNITED STATES PATENT oEEIcE,

BATTERY CHARGING AND VOLTAGE REGULATING SYSTEM Kurt Mullerheim, Chicago,.111., assignor toAuto.-

matic Electric Laboratories, Inc., Chicago, Ill., n u

a corporation of Delaware Application July 1, 1944, Serial No. 543,104 n22 Claims.

power bus bars of the exchange, and to which,

bus bars a storage battery and the exchange load are also connected inparallel. l The battery serves` as an emergency sup-ply source to theex-.

that one charger unit provides a low 1ate .charge`n` and both chargerunits ,multiplied together provide a high rate charge/any; oney ofthese' charging n methods incorporating vend""cellsll or not t" fcumstances may require. l

change load in case of charger failure orrco'm-v mercial power failure,supplies current to the load during peaks of tralicv when the currentdemand exceeds the output of the charging unit, and supplies current tothe load during other periods when current is not required from thecharging source.

An object of the invention is to provide an improved current supplysystem which includes new and novel means for automatically regulatingthe charging and the voltage of a storage battery, in order that thevoltage at the main power distributing bus bars may be maintainedconstant or, The

kept lwithin specied high and low limits. charging may be initiated ateither a low rate or a high rate, may be switched from a low rate to ahigh rate or vice versa, or maybe entirely disconnected, all of thesechanges being automatically controlled in accordance With the voltage ofthe battery in order thatserious overcharge may be avoided. a

Another objectief the invention is to provide an improved current supplysystem'` wherein voltage test equipment automatic in operation and novelin arrangement controls the operation of the charging equipment. 'Ihevoltage test equipmentr is not responsive to relatively minor orInomentary changes in the voltage of the storage battery which may causeneedless and `expensive cycling of the charging equipment, but respondsfaithfully to substantial andsustainedchanges infthefbattery voltage.

A further object of the invention is to'provide an improved currentsupply system whereinlthe charging equipment may consist of a singlecharger unit with one charging rate, one charger unitwith both a low'charging 'rate `and a high charging rate, or tvvo'charger units'soarranged Another object of theinventionA is tofprovide` an improvedmethod for cutting end cells in and out cfu the discharge circuit ofthe'storagebattery wherein the end cells arefswitched in to thedis-Ycharge circuit at a higher" voltage level "when a charged failure occursduring a highnratecharg-f ing period than the low .voltagle'limit`usedwfor regularly cuttinginthefend cells,

In order to accomplish .the above described ola- V jects, Athe currentsupply"sy ste in includes. a st orA-v.

lay or relays for connecting and disconnecting` the charger unitormunits, voltage test equipment for automaticallycontrolling theoperation ofthe. charger relay or relays,` "a chargerate switching relayunder the control ofthe voltage test equip-4 ment for switchingfrom alow rate of: charge to a high rate of charge and viceversa, a timer`unit for causing the voltage test equipment to test the voltage of the.battery periodically preparatory to starting the charging, changing thehargingvrate. or stopping the. charging, `end cells, i an `electro-1magnetic switch for cutting in or cutting'outthe end cells,and relaysunder the supervision `of the voltage test equipmentfor controlling theoperation of the `end cell switch, all suitably interconnectedtoprovidethe desired combination of facilities. j f f l A` feature'oftherinvention istlflt thevoltagc J of the system battery kept withinspecified high intermittently forhigh .voltage andcontinuously for4lowvoltage. l'Iworseparateandfindependent relays .are included in theWvoltage test` equip-` ment for testing the voltage. of `the batteryyOne of these relays is known as the high-voltagetest relay and isswitched-across the-battery fatperie` `odic intervals so long asthereisatracload on the systemfiorthe purpose 'of causingthe charg` ing `tostart,v the l rate of-charging tochange, the cutting oi Yof the charge;and the switching out of the end cells when end cells are employed.other relay'is known as 'the low-voltage test relay, and is bridged'permanently across the battery for the purpose of causing charging atthe high rate Whenever the voltage' Qf'hebattery drops ,t0 the..

f `preset flowlimit, and also `vfor causing the end cells! to` beIswitched intothe discharge circuit of the battery when end cells areused. Since the lowvoltage test relay is connected across the battery atall times, the battery is protected continuously against discharge belowthe low voltage limit, as the low-voltage relay will function whether ornot there is a traffic load on the system or Whether charging ispreviously in effect at a low rate.

Another feature ofu the invention is. that the` low-voltage test relayis fitted with acontact of the snap action type instead of with standardrelay contact springs. The circuits controlled Iby the low-voltage relayare, therefore, closed and opened with the rapidity of power relaycontacts, as the contact is retained in either the Y open or closedposition until reversed by snap action. Hence, there can be no creeping'or possible vibratory contacts as the relay is gradually energized ordeenergized.

A further feature of the invention is that the high-voltage test relayoperates at two different. high voltage valuesfor causing twoseparateand independent charge cut-offs. As is well known, in current supplyAsystems employing a high-voltagerelay, the relay is usually adjusted tooperate at one given highvoltage value only and, therefore, performsonly one function. In the present invention, however, the high-voltagetest relay. operates atonehigh voltage value to cause the cutting off ofthe high current rate of charge, and'then is automatically resetto op.-erate at afhigher value. for cutting off the low current rate of charge.

There are otherY objects and. features. not specifically mentioned, butwhich will become apparent by a perusal of the following descriptionwhichtogether' with'the twosheets of draw-Y ings, constitutes oneembodiment of the invention. Y

Referringl now to the drawings, Fig. 1 shows.

is titled Voltage test equipment and. includes` the equipment requiredfor controlling the charging of the battery and for regulating thevoltage delivered.y to the powerv distributing busbars., The equipmenttothe right is tilled End cell control equipment and isconcerneddirectly with controlling the switching of thel end cells.

When end cells are not to be employed,`the end cell control equipmentshown in Fig. 1 may be omitted, and the voltage test equipmentv willfunction properly to control charging, and bus bar'voltage when certainleadsl shown in Fig. 1

as interconnecting the two relay equipments are shorted together, otherinterconnecting leads are left disconnected, land certain minor changesare made, such relatively simple modifications beting readily apparent.to those skilled in the ar Fig. 2 when placed*V below- Fig'l, shows thepowerV apparatus common to the relay equipmentof Fig. l, In thesedrawings at 280 is represented a storage battery of 48 volts, forinstance, comprising 23.cells, with. which are associatedthe three endcells 285` The battery, or

CII

negative, bus fbar of the system from which battery current isdistributed is shown at 210, and the ground, or positive, bus bar at215. The battery bus bar 210 has its connection with the ungroundedterminal of the battery 280 by way of the short-circuiting arm 26| ofthe end cell solenoid switch 281. When the end cells 285 have beenconnected in series with the battery 280, the battery bus bar 210connection to the ungrounded terminal of the battery 280 is made via theshort-circuiting arm 269 of the solenoid switch 281. Should end cellsnot be employed, the end cell solenoid switch 281 and the end cellcharging switch 286 may be omitted, and the battery dous bar 210 is thenconnected directly to the ungrounded terminal of battery 28D. A load 255is shown bridged across the distributing bus bars 210 and-,215. Itshould be understood that the load 260 is comprised of a large number ofrelay and magnet windings, lamps and other elements, but for convenienceof eXplanation these elements may be lumped together and considered as aload of variable resistance.

At the upper left of Fig.,2 is shown .a rectifier 263 of the full-wavethermionic type, and below the rectifier arel shown power switching andsupervisory relaysA associated with the battery charging circuit. Itshouldbe understood, however, that the charging equipment may consist ofany well-known type, and also that two chargers arranged to be operatedin multiple may be employed.

While in the drawings Fig. 1 and Fig. 2 a plurality of batteryconnections are shown, it should be understood that they are preferablythe same battery. Also, in order to simplify the drawings further, usehas been made ofbasic conventions, and such well-known associated powerappliances as power panels, main power switches, fuses and supervisory.equipment have been Iomitted.

The invention having been described generally, a detailed operation ofthe equipment will now be given. For this purpose it will be assumedthat the battery 28B is. carrying the load 26!)V and that the voltage ofthe batteryy is within the prescribed low and high voltage limits. Withthis condition of operation, the equipment is in the position shown inthe drawings.

In order that the detailed. operation may be readily understood, thefollowing-twotables indicate the conditions under which the high voltagetest relay 20 and the low voltage testrelay10 will functionrespectively.

, High voltage test relay 20 Operate on 46 volts in series withresistances l1 and I8. v

Operate on 52 volts in series with' resistances I 1,

I8 and part of 31.

Operate on 53 volts in series with resistances I7',

I3 and a larger part of resistance 31.

It shouldl be noted that resistance. 31 is fitted with two adjustabletaps to obtain the 52 and 53 volt settings.

Low voltagevtest-relay Release on 44 volts in series with resistances 13and 14, and resistance 15 in multiple with resistance 13.

Release on 46 volts in series with resistances 13 and 14.

Release onl 48 volts in series with resistancesV 13 and 14, andresistance |11 in multiple with the coils ofrelay 1G and resistance 13in series.

It should be noted that resistances 13, 15 and |11 ,are tted withadjustable .taps to secure the voltage settings. L

Periodic .test for low voltage So long as there is a call going th'roughthe exchange, the timer 3 I, which may be of any we11- known type, willbe in operation alternately grounding the time l and time 2 leads`momentarily, as, for example, every 15 seconds. Thus, both time leads Iand 2 will be grounded atO second intervals spaced 15 seconds apart. If,on the other hand, there is no trafc in the exchange, the timer 3| wil1not operate and, consequently, the two time leads will not bealternately grounded. This arrangement provides for the periodictestingof the battery voltage, dependent upon whether or not calls arebeing made in the exchange.

Assuming there is trac in the exchange, relay 39 operates each time thetime lead I is grounded and locks to the circuit formed from positivebattery, contacts 43, II, 32, second winding of'relay 30to negativebattery. The locking of relay30 closes the circuit of relay 40 frompositive battery,V contact 35, contact I4, relay 45 to negative battery,and closes the circuit of relay 2|! from positive battery, contacts 35,46, 81, 63, |41, relay 2B, resistances I1 and I8 in series to negativebattery. Relay 4|! is slow to operate and, therefore, th'e circuit torelay 2|! is maintained for an inter; val at contact 46. i

If, under the conditions cited in the preceding paragraph, the voltageof the battery remains v above 46 volts, relay 2B will operate and closethe circuit of relay I0. The operation of relay' I0 short-circuitsresistance I1 at contact I 6 to insure relay 20 remaining operated:opens the locking circuit of relay 30 at contact II; and opens thecircuit of relay 4E) at contact I4, thereby preventing the operation ofrelay 40. Relay 30 restores and opens the circuit of relay 20 at contact35. Relay 20 restores and opens the circuitlto relay IU. short circuitfrom resistaice I1.

Relays 30, 2|] and I0 cycle as described above every 30 seconds so longas there is traiiic in the exchange and the battery Voltage remainsabove 46 volts.

Low current rate charge In time, as discharge of current from battery28o takes place, the voltage across the battery will drop to the lowlimit of 46 volts. When this occurs at an interval that time lead I isgrounded, relay 2|! will not operate responsive to its circuit beingclosed by relay 30, and relay III,4 therefore, cannot operate to openthe circuit to relay 44 Il at contact I4.` Relay'ltll, therefore,operates after a short delay and locks to positive battery throughcontacts I4 and 45.

The operation of relay 4ilunlocks relay 30 at contact 43 causing relay30 to restore: opens .the circuit of relay'ZI) at contact 46:closesthecirf, cuit of power relay 240 from positive battery, contact44, conductor 29|, relay 240 4to negative battery: connects the time 2leadthrough cntacts 42 and 5I to relay 56: closes `the circuit'off relay|95 from positive battery; contact4l, conductor 288, contacts 2| land22| in multipleLcon-.- ductor 289, Contact I4I, relay I9!)tgneiativebat-V tery; and adjusts the resistance of the circuitfof relay25 so that relay 2!) will not operate when its circuit is again closedunless thebattery Volt,- age has increased to 52 volts. TherestorationRelay I restores and removes the- M alternating current power circuit tothe rectifier 260 at contacts 243, 244 and 23|, and also extends thepositive charge lead from the rectier 260 to thepositive terminal of thebattery 280 through contact 232, 242 and 24|. Direct current at the lowcurrent rate because of th'e resistance 253 in thepositive lead nowcharges the battery, and supervisory relays 2|0 and 225 in 'the negativecharge leads are operated so long as the charging current maintains.Relays 2|0 and 220 are shunted respectively by resistances 2 I 2 and 222to permit by-passing most of the charging current around the two relays.The operation of relays 2 I0 and 220 opens the circuit of relay |90 atcontacts 2|| and 22| and the non-operation of relay ISD maintains th'echarge alarm circuit, which IIIaEy-be of any well-known type, open atcontact; A ground pulse over time lead 2 causes relay 50 to operatethrough.contacts 42 and 5|. Relayi locks to positive battery throughcontacts 52 and 44and is, therefore, under the control of relay 46, andopens the multiple circuit through resistance to the low-voltage testrelay 10 at contact 53. The circuit of relay 10 isnow adjusted to causerelay 10 to restore should the battery voltage drop below 46 volts.` d

High current rate charge As explained in the preceding paragraph, theresistance of the circuit of low-voltage test relay 10 has been adjustedto cause relay 10 to restore if the low current rate charge is notsuiicient to maintain the battery voltage above 46 volts. Therestoration of relay 10 is controlled solely by voltage drop, the traicthrough the exchange having no effecten this function.

Y The restorationof relay 19 responsive to the voltage dropping'below 46closes the circuit to relay 90 from positive battery, contacts 1|, I 15,relay 90 to negative battery. The operation of relay90 closes thecircuit of relay Il! through an obvious circuit, relay IID operating inturn and locking to `positive battery through contacts II2 and 93. Thelocking of relay I0 causes relay `|2|J to operate from positive `batterythrough contact III.

The operation of relay closes the circuit of relay 8l) from positivebattery through contact |22, and relay 80 locks t0 positive batterythrough contacts 82 and I2. The locking of relay 80 causes charge rateswitching relay 256 to operate from positive battery at contact 8|,conductor 290, relay to negative battery and shunt out resistance 253 atcontacts 25| and 252, thereby increasing the charging to the highcurrent rate:

causes relay 60 to operate from positive batteryA through contact 8|:short-circuits resistances 13 and 14 with positive batterythroughcontacts |26 and 83,- thereby causing relay 10 to operate byreason of the voltage through relay 1!) being raised by. theshort-circuiting of resistances 13 and 14: shunts out a portion of`resistance 31 at contact 88 to adjust the circuit of relay 20 to causethe operation of Arelay 20 at 52 volts when the circuit of -relay 28 isclosed; and closes the circuit of relay 2l] from positive battery,contact 36, part of resistance 31,7contacts 88, 41, 8B, |41, relay` 20,and resistances I1 and I8 in series to negative battery. The operationof A relay 69, of relay closes the circuit of relay 20 at con- 75` whichis slow to release, places a multiple holding ground on. relay 46 toiinsure relay 4.6 rernain.-v ing locked up.

The operation of the low-voltageztest relay'16, as described in thepreceding paragraph, opens the vcircuit to relay 96,` causing. relay 96to. restore. Relay 96 is fitted with a weighted spring which is set invibration when the relay restores, the weighted spring graduallycomingto a 'stationary position. As the weighted spring vibrates, groundpulses are sent to the slowetorelease relay. H6, these pulses becomingslower and slower and finally subside as the weighted `springcornes torest. The purpose of holding relay |||l` in the operated positiontemporarily is Ato allow the high current charging to raise the voltageof ,battery 286. When the vibrating spring of relay 96 comes tov rest,the circuit of relay |26 is opened.

The restoration of relay |26 removes the ground shunt to resistances 13and 14 at contact |26, and causes relay |36 to operate from positivebattery, contacts i2, 82, |23, relay|36 to negativebattery.' Relay |36locks to positive battery through contacts |36, 82 and |2. connectspositive battery through vcontact mem bers 261 and 266 short-circuited.bymember 262 of end cell switch 261, conductor 291, contacts |36, |94,84 to resistance 15, thereby adjusting the circuit of relay r16 to causerelay 1.6 tov restore 'should the battery voltage drop to 44 volts.

Mounted adjacent to the low-voltage'test relay 16 and connected inseries with the, coil windings of the relay is a negativetemperaturecoeiiicient resistor 12 for Athe purpose of compensating for changes inthe ambient temperature of relay 16 and thus prevent improper operationof the relay. As is well known, this type of resistor has the propertyof changing its resistance inversely as the temperature changes, i. e.,as the temperature drops, the resistance-is increased, and vice versa.Hence, because of the fact that the resistor is connected in series withthe windings of relay 16, a decrease in the resistance ofthe relayduetodrop in the ambient temperature is compensated for by a correspondingincrease in the resistance of resistor 12 and, therefore, relay 16 willfunction at the predetermined low voltage'value to establish the highcurrent rate of charginginstead of waitingto function at a still lowervoltage value. The battery 236 is thus protected against dis-v chargebelow the low voltage limit when the ambient temperature is relaitvelylow.

End cell cut in If the voltage of battery 266 should drop to 44 voltsVwith chargingV at the high current` rate, relay 16 will restore andcause relay 66 to operate :from positive battery, contacts 12 |15, relay96 to negative battery. The operation of relay 66 closes the circuit ofrelay |66 through an cbvious circuit, relay |56 operating in turn andlocking to positive battery through contacts ||2 and 63. The locking ofrelay H6 causes relay |26 to operate from positive battery throughYcontact lll, and relay |26 locks from positive battery, contact members263 and 266 shortfcircuited by member 262 of end cell switch 281,conductor 292, contact |3|, contact |2|, second winding of relay |26 tonegative battery.

The locking of relay |26 causes relay E56 to operate from positivebattery, Contact members 263 and 264 snort-circuited by member 262 ofend cell switch 26,1, conductor 262, contacts |35, |24,

through contacts |26 and '83 vthereby causing The lockingl .of relay|66' relay 16 to operate; `and connects'positivebattery to the end cellsupervisorycircuit, which maybe of any well-known type, throughcontactsIE, |35and |26.y

The operation of relay 16 opens the circuit to relay96 at contact 1|which in turn restores and sets its weighted spring in vibration,sending ground pulses to relay H6, The operation of relay |56 closes thecircuit of the 26 cell magnet of end cell switch 281 over conductor 294,causing the Aend cell switch to move its short-circuiting members 26 I,262 and 266 to the left.

Member 26| disconnects the ungrounded terminal of battery 286 fromnegative bus bar 216, and member 269 connects bus bar 216 tothe negativeterminal-of end cell #26, thus connecting the lthree end cells 265 inseries with battery 286 and boosting the battery voltage by the voltageof the end cells.

Theshifting of member 262 to the left removes the holding ground fromrelay |26, the operating ground from relay |56, disconnects ground fromresistance 15,*a'n'd closes the circuit of relay |16 from ground,lmembers 263 and 265 shorted by member 262, conductor 293, contact |62,relay |16 to negative battery. Relay |16 operates and locks to positivebattery through Contact |1|, conductor 296, and members 265, 262 and263.

The locking of relay |16 causes relay |66 to operate through contact|12, andconnects resistance |11 through contact |16 and resistance 13 inparallel with relay 16. The |11 resistance in parallel with relay 16adjusts the circuit cf relay 16 after relayl |26v releases to causerelay 16 to restore should the battery voltage drop to 49 volts with theend cells 265 in series with battery 286. The operation of' relay |66opens the end cell supervisory circuit at contact |64, closes a multiplelocking circuit for relay |36 through contacts |62 and |33, and closes amultiple locking circuit for relay 86 throughcontacts |62, |36 and |34.

The restoration of relay |56, which is slow to release and does Vnotrestore until the end cell switch 261 has completed its shift to theleft, opens the circuit of the 26 cell magnet 4at contact |5|. The endcell switch 281, therefore, remains in the shifted position until the 23cell magnet is operated later.

Relay ||6 restores as a result of the weighted spring of relay 96comingv to'rest, and opens the operating circuit of relay |26 at contactThe restoration of relay` |26 completes the adjustment of the circuit ofrelay 16 vfor causing relay 16 to restore should the voltage of thecombinedbattery and end cells drop to 46 volts. The restoration'of relay16 as a result of the voltagedrep-` ping to 48 volts would cause theclosing of the low-voltage alarm circuit, which may be of any well-knowntype, through contacts 1| and |14.

End cell cut'oy The end cells 285 will remain connected in seriesY withbattery 286 until charging at the high current rate raises the voltageacross battery 286 to 52 volts Assuming there is traic in the ex change,the high-voltage test relay 26 is switched across battery 286 at 36second intervals, in the manner described in the first two paragraphs inthe section titled Periodic test for low voltage. When'the voltage ofbattery 266 reaches 52 Vvolts,.relay 26 operates and closes the circuitof relay I6. The operation of relay. llcau-ses relav |40 to operate frompositive battery, contacts I3,

j |25, |65, |63, relay |46 to negative battery, relay |40 locking to`positive battery through contacts |46, |66, conductor 296, members 268,262 and 261 of end cell switch 281 to positive battery.

The locking of relay I 46 opens the circuit of relay 26 at contact |41,causing relay 26 to restore and open the circuit of relay I6: closes theend cell `supervisory circuit from positive battery through contacts |63and |44: close-s a multiple circuit to relayi|16 at contact |43; andcauses relay |86 to operate from positive battery, members 261, 262 and268 of end cell switch 281, conductor 296, contacts |66, |46, |45, relay|66 to negative'battery.

The operation of relay |86 closes a circuit to relay |46 at contact |82:connects positive battery through contacts |83 and 83to relay 1 ahead ofresistance 13, causing relay 16 to remain operated; and closes thecircuit of the magnet 23 of end cell switch 281 through contact I8I overconductor 295, causing the end cell switch to moveits shortlcirc'uitingmembers 26|, 262 and 269 to the right.

Member`269 disconnects the end cells 285 from negative bus bar 216, andmember 26|connects the ungrounded terminal of battery 266 to bus bar216, thus removing the end cells 285 from battery 286y and reducing thebattery voltage by the voltage of the end cells.

The shiftingof member 262 to the right opens the'circuit to relay |66and one winding of relay |46' at member268; and connects resistance 15in Aparallel with resistance 13 frompositive battery, members 261, 262and 266, conductor 261, contacts |36, |94 and 84. i

The restoration or relay |86, which is slow to release and does notrestore until the end cell switch' 281 has completed its shift to theright, opensthe' circuit of'the 23 cell magnet at contact |3| opens thecircuit to a winding of relay |46 at contact |82, thus causing therelease of relay |46 since the circuit of the other winding of relay |40is already open at member 268 of the end cell switch; and removespositive battery from relay 18; I A i Therestoration of relay |46 opensthe end cell supervisory circuit at contact |44; and opens the circuitof relay |16 at contact |43, thus causing relay I16'to' restore sincethe multiple-locking circuit to relay I16`is already open at member 265of the end cellswitch.

The restoration of relay |16opens the circuit to relay I66'at contact|13; rand removes resistance |11 from'the circuit vof relay 16, thusadjusting the circuit of relay 10 to cause relay 'I6 to restore andcause the end cells 285 to be again connected in series with battery 286should the voltage across battery 286 drop to 44 volts.

currentrate chargecut off Assuming that the voltage of battery 266`doesnot drop to 44 volts after the end cells have been cut o i as describedin the preceding sectiontitled End cellcut off, the voltageA will inktime again rise to 5'2volts. The circuit of relay 26 has beenpreviouslyadjusted to cause relay,` 26 to operate Whenthevoltage ofbattery 286 reaches 52 volts.

vNowiassuming there is trame inthe exchange, the high-voltage test relay26 is switched across battery 286 at 36 second intervals,. in the mannerdescribed-in the rst two paragraphs in the section titled Periodic testfor low voltage. When' the Voltage ofbattery 286 reaches 52 volts, relay2 6 operates and closes the i circuit of relay I6. 'I'hejoperation ofrelay -I6 opens the locking circuits of relays 8 6 andv |36 at contactl2: opens a multiple circuit to relay 46 at contact I4; and closes amultiple circuit to relay 26 at contact I5. Relay 86 restores and opensthe circuit of relay 26 at contact 86: removesthe short circuit aroundpart of resistance 31 at contact 88 thereby adjustin-g the circuit ofrelay 26 tocause relay 26 to operate when the voltageof battery 266reaches 53 volts: removes resistor 15` from the circuit of relay 16thereby adjusting the circuit of relay 16 to cause relay' `16 torestoreshould the` battery voltage drop to 46 volts; opens the circuit torelay66 at contact 8|; and opens the circuit to power rategchanging relay; 256 at contact 8| thereby causing relay 256 to restore and reducethejcurrent charging rate by removing the short circuit from resistance253 at contacts 25| and 252.

Relay 66 is slow to release and, therefore, maintains the circuit torelay 46 at contact 6| suciently long to permit relay I6 to restore andclose the multiple circuit to relay 46 at contact I4 before contact 6|opens. The restoration of relay 66 also closes a' circuit for relay 2 6at contact 63.`

The restoration of relay 26 opened theA circuit to relay |6 at contact2| and causedrelay I6 torestore. Relay I6 is fastfacting in'releasingand, as stated in the preceding'paragrapli, establishes a holdingcircuit to relay 46 at 'contact |4 before relay 46 has suicient time torestore.'

As a result of relay 46remaining in the oper-` atedl position, relay 56`remains locked to. positive battery at contact 44 andlpreventstheclosureof the circuit to resistanceV 15 atfcontact 53. .The cir-`cuit of relay 16, therefore, remains adjusted to cause relay 16 torestore whenever the battery voltage drops to 46volts. f l

Low current rte charge ctoj Assuming that ktl 1e vol'tage of battery 6does not drop |1046 volts afterthecharging `has` been reduced to the lowcurrent rate,` as described in the preceding section titledVHigh currentrate charge cut oil, `the voltage time will riseto53 volts;` Thecircuito@ relay26 has been previously adjusted to cause relay 26 tooperate whenthe voltage of battery 286 reaches 53 Volts.

Now assuming there is traiiic inthe exchanga,

the high-voltagetest relay`20 isv switched `across battery 286 at 30secondintervals, ,inrthemanner described inthe firsttwo paragraphs inthe` section titled.,Priodic test fori lowi voltage .1

In this instance, however, the-,circuit to relay `26 is opened atcontact 36 when relay 36 operates momentarily, thus preventing thepossibility of relay 26 operating prematurely, Whenthe voltage' ofbattery 286 reaches 5 3A Volts, relay 2 6 operates and closes thecircuit to relay. |6. `The operation of relay 'lpens thecircuit to relay46 at contact I4, threby'causing relay V46 to restore;

and closes amultipl circuit to relay A26 at con-I tact I 5 so' thatrelay 36 Qwill not open the circuit to relay26.

The restorationof relayflldisconnects power relay 240 at contact 44,`thereby causing relay;

246 to restore and open the charging circuit at contacts243 and 244f`for the'primary side and ing current,l rI 'he charge alarm'supervisoryA cir? cuit is Vthus retained in the open position atThe'lack of charging current through relays 2||J and 220 closes contacts'2H and 22| but, as explained in the preceding paragraph, the circuit'to relay |90 is open at contact 4|.

yThe Vrestoration of relay 59 connects positive battery to resistancethrough contacts 53 and `85, thereby adjusting the circuit oflow-voltage test relay 'lll 'to cause relay 4T0 to restore should thebattery voltage drop to 44 volts. The restoration of relay opens theYcircuit to relay I|l-at contact 2l and relay I0 restores.

The battery charging and voltage regulating circuit iis now atnormalwith the end cells disconnected and no charging. The next cycle ofoperation is started as explained in the section titled'iPeriodic testfor low voltage.

Generali features The end cells 285 may be charged along with thebattery by operating the hand-controlled end cell switch 286 so as toconnect the end cells in the negative charge' leads in series withbattery 285. This feature is independent of the automatic end cellcontrol, and the end cells may be 'charged whether they are connected tothe negative bus bar 210 Vor not.

`Condensers 33 and 95 are connected in series respectively withresistances 34 and S to prevent excessive sparking at contacts 44 and 8|when the circuits to the power relay 240 and the charging rate switchingrelay are opened.

'Con'densers |52 and |84 are connected in series respectively withresistances |53 and |85 to prevent excessive sparking at contacts |5I,and |81 when the circuits to the end cell magnets are opened.

A flash over relay 230 is associated with the tube-type charger 260. Incase a tube fails and causes an abnormally Vhigh-current to flow in thealternating current power circuit, relay 23|)` will operate to open thepower circuit at contact 23|, and the -positive charging lead at contact232. Either supervisory relay '2|0 or 220 or both will restore becauseof lackof charging current and close the `circuit yto relay |90 atcontacts 2|'| and/or -22=|, andthe 'operation of relay |90 will closethe charge alarm supervisory circuit at con- Y tact gras.

'Having described the invention and' what is considered new and desiredto be protected by Letters-Patent is set forth in the `following claims.

What is claimed is:

`1. -In a battery charging system, a storage battery,.charging means,means in bridge of 'said battery and responsive at all times to thedropping of the voltage across said battery to a predetermined -valuefor causing said-charging means to chargesaid battery, lanelectromagnetic voltage testing device, means for bridging said deviceacross said battery at periodic intervals, and means responsive vto theoperation of said device by reason of the voltage across saidbattery'rising to a'predetermin'ed value for disconnecting said chargingmeans from said battery.

2. In abatteryeharging system, a storage battery, a charging circuit forsaid battery, means permanently'in bridge of said battery and responsive-to the dropping of the voltage across said battery toa predeterminedvalue for controlling said charging circuit to cause the charging ofsaid battery, an electromagnetic voltage-testing device,'a timingelement operative continuously for generating 'electrical pulses at`uniformly spaced intervals, means .responsive to the pulses fromsaidtiming element for switchingsaid device across said-battery at saidspaced intervals, and means responsive to the operation of said deviceby reasonof the voltage of said battery rising to a predetermined valuefor opening said charging circuit.

3. In a battery charging system, a storage battery, a charging circuitfor said battery including means for charging at different currentvalues, means permanentlyin bridge of said battery and responsive tothedecreasing of the voltageacross said battery to a predetermined valuefor controlling said charging circuit to causethe charging of said-battery at the highest current rate, an electromagnetic voltage testingdevice, means operative periodically for switching said device acrosssaid battery, said device arranged to oper.

ate in response to the voltage across said battery rising to apredetermined value, and meanscontrolled bysaid device for reducing therate of charging current.

4. In a battery charging system, a storage battery, charging means, anelectromagnetic voltage testing device, switching means operative.atperiodic intervals for kbridging said zdevice across said battery totest the battery voltage at said intervals, said switching meansincluding -an operating circuit for said device normally arranged toprevent the operation of said device'when the voltage across saidbattery tests below a predetermined value, and means operated in theevent of the non-operation of said device during a testing period byreason ofthe voltage across said battery decreasing below saidpredetermined value for causing said charging means to charge saidbattery, and for Vre-arranging said operating circuit to prevent saiddevice operating during a subsequent testing period unless the voltageacross said `battery rises to a predetermined high limit value, theoperation of said device responsive to the rising of the voltageacross'said battery to the said predetermined high limit value causingsaid charging means to be disconnected.

5. In a battery charging system, a storage battery, means for chargingsaid battery at different current values, two electromagnetic voltagetesting devices,one of said devices permanently bridged across saidbattery and arranged to operate in response to the voltage across saidbattery decreasing to a predetermined low value for causing saidcharging means to chargesaid battery at the highest current rate, meansoperative periodically for generating `electrical pulses, meansresponsive to said pulses for switching the said second device in bridgeof said battery, said second device arranged to operateV in response tothe voltage across said batteryrising to a predetermined value, andmeans controlled by 'said second device for reducing the chargingcurrent to a lower value or for disconnecting said charging means.

6. In a current supply system subject to variable load current demands,a storage battery, means for chargingsaid batteryat a `low current rate0r a high currentkrate, two electromagnetic voltage testing devices,means operative at periodic intervals for connecting the rst of saiddevices in bridge of said battery at said intervals to test they voltageof said battery, means controlled by said rst device by reason of thevoltage across said battery beingbelow a predetermined low value duringatesting'period for causing said charging means to charge said battery atthe low current rate, a closed circuit permanently bridging said seco-nddevice across said battery -to test continuously Afor low voltage, saidsecond device arranged :to operate responsivel toY r the decreasing ofthe voltage of said battery bef. lowsaid lowvalue because of aheavy'load current demand, and means controlledbysaid sec-n ond devicefor increasing the charging to the s aidl high current rate, l

11n a current supply systemastorage batltery,.means for charging saidbattery at a ylow current rate or ahigh current rate, two electra-,-

magnetic voltage testing devices, means operativeA at `periodicintervalsfor connecting the rst of4 lished' providing the voltage .across saidbattery` rises to apredetermined high` limit value, a clsed` circuitpermanently bridging said `second device, across said battery, saidsecond device arranged to operate responsive to the decreasing ofthevoltage ci said batterybelovv said low value, and means controlledbysaid second device for in-, creasing `the charging `to the said `highcurrent rate, the operation of said iirstdeviceresponsive to the risingof the voltage of said battery to the said high limit value causing saidcharging means to be disconnected.l e i 8. Ina current supply system, astorage'battery, means 'for charging said battery at a *low` currentrateor a high current rate, two electro. magnetic voltage testingfdevices,means` opera-v, tive at periodic intervals for connecting the rst ofsaid devices,acrosssaidbattery at said intervals, means controlledbysaid'iirst deviceuby reason of the voltage of `said battery. decreasingte a predetermined low value for causingsaid charging means to chargesaid battery at the W current rate, means for resetting said rst de-`vicefto operate in a subsequent testperiod after! saidlovr currentcharging has been established;

providing the voltage of said battery rises to ar predetermined highva1ue,"a closed circuit permanently bridging said second 4device acrosssaid, battery, said secondfdevice arranged to operate responsive to thedecreasing of the voltage of said` batterynbelowi said low value, meanscontrolled byjsaid second device for increasing thecharging'to the saidhigh current rate, theoperation of said first device responsive toV therising of the Y voltageacross said battery tothe said high value causing-the'charging' to, be reduced to the said low current rate, and meansforresetting .said

rstdevice tooperate in a subsequent test period,

after said lowcurrent charging has been re-established providing thevoltage of `said battery rises to a high limit value greater than saidhigh value, the re-operation of said iirst device responsive to,therising of the voltage :across said battery `to the said high limitvalue causing the disconnection of said charginglmeans.

9. In a `current supply System, a storage battery, means for chargingsaid batteryat a low` current rate 'or a highl current rate, twoelectrof magneticv voltage testing devices, means operative ,at periodicintervals for connecting the Arlrst oflsaid devices in bridge of saidbattery` at said intervals, a closed circuit permanently: bridging saidsecond device across said battery, said second device arranged to lbecontinuously oper-` atednso long asy the voltage' 'or said batteryremains above, a predetermined low i value, rneans www..

at the said low current, rate, the voltage decrease to said low value,also` causing said second. device to restore, means responsiveu to therestoration of Isaid second device for changing said circuit tocausesaid second device to re-operate, and for resetting said seconddevice to restore again if the voltage ofgsaid `battery decreases belowlsaid low value for increasing the charging to the said high currentrate, and means for resetting said iirst deviceto operate in asubsequent test period providing thevoltage across said battery rises toa predetermined high value,;the operation of said irst device responsiveto the rising of the voltage of said battery to said highvalue causingsaid charging means to bedisconnected.

10, In a currentsupply battery, a storage battery, means forchargingsaid battery at different current rates, an`electromagnetidvoltage testing device, a closed circuit permanentlybridging said deviceacross said battery, said device arranged tonbecontinuously operated so long as the-vo1t` age across said batteryremains above a predeter-f mined low -Valuameans responsive to theArestora-` tion of saiddevice by reason of the voltage across said;batterydropping below said low value for causing saidvcharging means tocharge at the highest current ratenfor causing said device to reoperate,and `for resetting said device 4toirestore battery again decreasingbelow said low rate causing `a low voltage alarm circuit tolbeioper-`ated.' i

, l1, In, combinatioma sourceoffelectric power,

an electromagnetic device, a circuit connecting said device to saidsource, said circuit including resistance of such value to cause theoperation of said `deviceat a predetermined voltage value and therestoration, of said device `responsive to the` decreasingof the voltageto a predetermined low l-Value, a `separate resistance, and Ameans `forconnecting said separate `resistance in multiple with s said resistanceincludedin saidcircuit, said separate resistance of suchgvalue thatthevoltage supplied to said device by reasonofthe two said -resistancesbeing connected in multiple is surri-` ciently increased to cause` saiddevice to re-op'erate. i n l flZl` In combination,. a source of electricpower,

two electromagnetic devices, oneof said devices connected in bridge ofsaid source and arranged to be operated continuously so long as thevoltage across said source remains above apredetermined low .,va1u eandmeans connecting said second device across'zsaidsource at periodicintervals, said fseconddevice arranged to operate during said intervalsonly lin the event .that the voltage across ksaid source `remains abovesaid lowvalue.

`In r'ernbination, `a storage battery, means foruchargirng saidbatteryateither a low current rate or a highcurrent rate,;tW0,electromagneticdevices, the rstofrsaid- `devices controlling the said lowcurrentratecharging and the said seccreasesrto a, predetermined low value` forcausing said charging 1means to chargersaidbattery at said low currentrate said second deviceineffective to cause; said charging tobeincreasedt'o the l across said 4battery does not drop-below said'low value, andImeans for resetting said first device to cause the `disconnection ofsaid vcharging means responsive to the rising of thevoltage across saidbattery to a predetermined high value.

' 14. In a telephone System,`a storage battery, aV

discharge circuit therefor, subscribers "lines, means lincluding saiddischarge circuit for completing connections between saidlines, chargingmeans, means in bridge of said battery and responsive at all times tothe dropping of theV voltage across said battery to a predeterminedvalue for causing said charging means to charge said battery, anelectromagnetic voltage testing device, means forswitohing said deviceacross said battery at periodicintervals only so long as there areconnections between said lines, andA means responsiveto the operationofY said device -by reason of thevoltage'of said battery rising to apre-A determinedvval'ue for disconnecting said charging means. Y Y

, V15. In a Vtelephone system', a storage battery, a discharge circuittherefor,- subscribers lines, means including said discharge circuit`vfor completing connections between said lines', acharging circuit forsaid batteryincluding means for charging' at different current values,meansresponsive to the'decreasing -oi the-voltageacross said'battery toa predetermined value for controlling said Vcharging circuit' to causethe charging of said battery at the highest current rate, anelectromagnetic-voltage testing device, means for switching' said deviceacrosssaid discharge circuit at periodic intervals only so long as thereare connections between said lines, said device arranged to operate inresponse to the voltage across said battery rising to a predeterminedvalue, and means controlled by said device for' reducing the chargingcurrent to a lower value or for opening said disch-arge circuit. i f v16. In a telephoneV system', subscribers lines, means .for establishingconnections between said lines, a storage battery, an electromagneticvoltage testing-device, and means voperating at periodic intervals byreason of one or more connec-v tions existing oifbeingestablishedrbetweenisaid i lines for switching said device across said battery totest the voltage of said battery at said intervals.

17. Ina telephone system, subscribers lines,

means for completing connections between said lines, a storage battery,charging means, an electromagnetic voltage testing device, switchingmeans operating at periodic intervals byreason of one or moreconnections existing or being established between said lines forbridging said device 'across said battery :at'said intervals to test thevoltage of said battery, an operating circuit for said device included.in said switching means normally arranged toprevent the operation ofsaid device when the 'voltageacrossA said battery tests below apredetermined value, means operating in the event of thenon-operationf'off YsaidV device during a testing period by reason ofthe voltage across said battery'decreas'ing below said predeterminedvalue for causing said charging means to charge said battery andtorre-arranging said circuit to prevent said device operating during asubsequent testing period unless the voltage of saidv battery rises toapredetermined high limit Value, the operation of said device ina testingperiod responsive to the voltage-across said battery rising to the said'predetermined high limit genesis said Ahigh-current rateso" long as thevoltage value fcausingsaid charging means togbe discon-v nectedfrom saidbattery.V Y

A318; InV a telephone system, subscribers lines, means'forl completingconnections between said lines, -a storage battery,vmeans for chargingsaid battery, two electromagnetic voltage testing devices,`one jofsaid-devices permanently bridged across saidbattery and responsive tothe decreasingfof the voltage across said battery to a predeterminedlowV limit value forcausing said charging means tor start charging saidbattery, means operatingl periodically by reason of one or moreconnections existing or being established between said lines for`generating electrical pulses, means responsive to said pulses forswitching said second device-across said battery to test the voltageacross said battery at said intervals, said second-deviceV-meansinbridge of said battery and responsive toV the decreasing of thevoltage across said battery to a vpredetermined lowvalue for causingsaidcharging means to 'charge .said battery, means for resetting saidswitching means after the voltage across said battery has decreased tosaid low value to cause the switching of said end cells in series withsaid battery should the voltage'across said battery drop below said lowvalue, said switching means responsive to the decreasing of the voltageacross Vsaid battery below said lowvalueY subsequent'to theestablishment of said l charging causing said end cells to be switchedin series with said battery, an electromagnetic Voltage testing' device,means for bridging said device across said battery at periodicintervals, and means responsive to the operation o f said device byreason ofthe voltage ofsaid' combinedbattery and end cells rising i to-apredetermined high value for disconnecting said end cells from saidbattery.

20. Inja current` supply system, a storage battery, "charging means, endcells, switching meansdnl' bridge yof saidbattery and responsive to thedecreasing of the voltage across said bat- "tery toa predetermined lowvalue for causing saidlovv valueto cause the switching of said end cellsin series with said battery'should the voltage of said batterydropfbelow Vsaid low value, said switching.meansresponsive tothedecreasing'f'of the voltageacross said battery below said low-valuesubsequent to the establishmentY of said 4charging causing said endcells to be switched-in 4series with said battery land thereby raisethe=voltage of said battery by the added voltage of said end' cells, andmeans responsive to the decreasing ofthe voltage of said Vcombined'battery and end cells below a predetermined value for causing a lowvoltage alarm circuit to be operated.

21. In a current `supply system, a storage battery, charging meanshaving acharging position, end cells, means Yin bridge of Said batter7and responsive to the decreasing of the voltage across sai'dbatter'y toa predetermined low value for 'switching said charging means to thecharginglposition,` and means'operative by reason of the fai-lure of4said `charging means to supply charging current to said battery forcausing the immediate switching of said end cells in series with saidbattery.

22. In a telephone system, subscribers lines, means for completingconnections between said lines, a storage battery, charging means, endcells, switching means in bridge of said battery and responsive to thedecreasing of the voltage across said battery to a predetermined lowValue for causing said charging means to charge said battery, means forresetting said switching means after the voltage across said battery hasY said low value, said switching means responsive to the decreasing ofthe voltage of said battery below said low value subsequent to theestablishment of said charging causing said end cells to be switched inseries with said battery, an electromagnetic voltage testing device,means for bridging said device across said battery at periodic intervalsby reason of one or more connections existing or being establishedbetween said lines, and means responsive to the operation of said deviceby reason of the voltage of saidcombined battery and end cells rising toa predetermined high value for disconnecting said end cells.

KURT MULLERHEIM.

